Many conventional internal combustion engines are configured to provide lubricating oil that sprays the cylinder walls or piston liners over which the piston rings travel during the stroke of the engine.
In some 2-cycle engines, such as the “Internal combustion engine with a single crankshaft and having opposed cylinders and opposed pistons” (“OPOC engine”) described in my U.S. Pat. No. 6,170,443 and incorporated herein by reference, lubricating oil is pumped through passages in the crankshaft and connecting rods to the piston pins. Conventionally, crankcase oil is splashed into the cylinder area below the piston rings to effect wetting of the liner surfaces. In such lubrication systems, the piston rings pick up the lubricating oil as they pass over the wetted liner surfaces and carry it forward as the piston travels from bottom dead center (“BDC”) towards top dead center (“TDC”). With each stroke, a small amount of oil is carried past the exhaust and inlet ports of the cylinder.
There is a need for improved lubrication systems as they apply to 2-cycle engines, since if the liner is too wet, the piston rings carry too much oil forward into the scavenging ports and into the combustion chamber. This results in loss of oil through exhaust ports that can result in HC emissions. Also, the moving of oil past intake ports causes some oil to be carried into the combustion chamber, which may alter the combustion process. Conversely, if not enough oil is transported to the piston rings, then excessive wear may result.
In my U.S. Pat. No. 7,735,834, which is incorporated herein by reference, a non-moving oil seal is disclosed that is mounted in the cylinder wall immediately below the exhaust/intake port to ensure both gas and oil tightness.
In my U.S. Pat. No. 7,509,937, which is incorporated herein by reference, a lubrication system includes an inertia pump within a piston that reacts to changes in inertia of the piston as it reaches TDC. The change in inertia causes the pump to react and force a predetermined measure of oil into the space between the piston and its adjacent cylinder wall immediately below the upper piston rings.
In my non-provisional application Ser. No. 12/583,916 referenced above, a small reservoir is contained in the piston that is filled when the piston is near its bottom dead center (“BDC”) position and piston inertia is utilized to inject the proper amount of oil from the reservoir into the space between the piston cylinder liner and the lower piston ring of the upper set of piston rings near the piston crown as the piston is completing its compression stroke on its way to reaching TDC. This point of injection causes lubricating oil to effectively lubricate the top of the travel of the piston rings above the intake and exhaust ports and allows the injected lubricating oil to be drawn down the liner walls in a controlled manner.